Keeping communications secret from an adversary or competitor has long been the challenge of the military, agencies of the federal government as well companies that are targets of corporate espionage. The challenge becomes even more difficult when communications are made from locations that do not have structures that have been built to prevent eavesdropping and the like, such as when a member of the presidential cabinet, foreign service or military travels to a foreign country, works in an embassy built by some other country or travels to a locale within the United States that is not considered secure from a communications point of view. Further, when secret or secure communications are required on the battlefield or in battlefield-like conditions a secure structure may be difficult to construct.
Secure enclosures that protect against electromagnetic interference (EMI) and radio frequency interference (RF) have been in operation for more than fifty years. Originally these enclosures were made of rigid metal panels, beams and doors and were typically prefabricated and shipped to a site were they would require a number of skilled experts to erect. More recently, shielded tents that can be transported in cases and quickly erected were introduced. Still, these tents require the use of a metallic support structure (e.g. beams, etc.,), integrated power and signal filters, waveguide vents, environmental control units (e.g., blowers, air conditioners, heaters). These tents are also bulky and require many transport cases for shipment and deployment. Just the weight of the empty transportation cases for a typical 7×7×7 enclosure could be in excess of 100 lbs, while the total weight of the system could reach 300 lbs.
Even more recently, support frames made from rigid aluminum tubing which can be erected with simple tools, angle connectors and/or articulated tubing have been introduced. These frames work well but are still relatively heavy and require large transport cases to store the longest components. Further, even the most efficiently designed aluminum frame still requires multiple individuals to construct. Yet further to attach a tent-like, shielded material to such a frame requires reinforced attachment points sewn into a roof section and into the corners that form an enclosure. In order to avoid stressing the stitching of the shielding material, which creates small holes that reduce the attenuation of high frequencies, the shielded material is stitched into a strong outer shell, typically made of a nylon fabric. However, this outer shell or skin is heavy, making it difficult to fold and, thus, requiring a larger and heavier transport case or cases.
Waveguide vents (WGVs) and power and signal panels must be attached to, or otherwise formed within, the shielded material through which connections to external power, signal and air supply components are made. To do so, great care must be taken so as to assure electrical conductivity between the fabric making up the flexible, shielded material and the typically rigid material making up a panel. This connection is almost always a weak point due to the challenge of connecting a rigid material to a flexible one. Many times the weight of the vents or panel along with their associated components stretches the flexible fabric and creates a tear or a distortion. While the installation of reinforcement patches on the surface of the flexible fabric may reduce tearing the patches add weight and reduce the flexibility of the material making it difficult to fold.
Accordingly, it is desirable to provide extremely lightweight and secure enclosures that provide at least the same level of EMI/RF, Electromagnetic pulse (EMP) and infrared protection (i.e., attenuation) as existing enclosures, but overcome the problems associated with the existing enclosures.